This invention relates to a pack of self-opening serially-arranged plastic bags of the xe2x80x9cstar-sealxe2x80x9d type particularly suited for use in packaging grocery produce and adapted to be suspended in desired lengths from a rack for being serially opened and removed from the rack.
Plastic bags have been replacing paper bags in the United States since the 1970s (and elsewhere more recently) in the grocery and retail products industries due to the superior and inherent moisture resistant properties and strength of plastic. In these industries, these plastic bags have usually included integrally connected front and rear wall portions and, sometimes, gussetted side wall portions, all secured together at the bottoms thereof by a seal to define a closed bottom on the bag. The bag walls are open at the top to define a mouth portion on the bag. Some of these bags are of the xe2x80x9cT-shirtxe2x80x9d type which provides spaced integral handles laterally extending upwardly from opposed sides of the open mouth of the bag at the top to provide ease in carrying of the bag by the consumer. However, these plastic bags have also included handless generally flat top rectangular shape bags, similar to the prior paper bags, without upwardly extending handles. These plastic bags have been provided to and used by the grocery and retail product industries in the form of packs of a plurality of superimposed bags connected together and adapted to be serially opened and removed from the rack, or in the form of a roll of plastic bags connected end-to-end and mounted on a rack to be serially removed and opened up, for packaging of the grocery or retail products.
The produce bag market in the United States grocery industry has been dominated over the years by plastic bags on a roll. These bags are typically manufactured of LDPE or HMW-HDPE in gauges from 0.50 to 0.35 mil. The biggest complaint with this style bag by shoppers is the difficulty in getting the bag opened. Grocery produce bags have been introduced of the HMW-HDPE construction which utilize a xe2x80x9cstar sealxe2x80x9d to close the bottom of the bag. The xe2x80x9cstar sealxe2x80x9d design (well known in the industry as a bag having multiple layers and longitudinally folded over on itself and sealed at the bottom so that when it is opened up, the bottom of the bag viewing from the inside resembles a star) got its start in the HMW-HDPE can liner market because of the excellent bottom seal strength it offers with thin gauge films.
Grocery produce bags of this star seal type have been accepted in part because of their strength, but also because they are somewhat easier to open than the traditional roll produce bags. Openability of this star seal type bag is improved due to the increased number of layers of film at the bag mouth. Notwithstanding, the shopper still mistakes the bottom of the bag for the top of the bag leading to frustration in opening of the bag. For the most part, these star seal type plastic produce bags have been provided in the roll form, although some bag packs of superimposed star seal type bags have been proposed. However, to applicant""s knowledge, all of the original bag packs of star seal type bags have been connected at the bottoms of the bags and suspended from a rack bottom-side-up so that the user must first remove the bag from the bag pack and then open the bag prior to loading of produce therein. This arrangement has presented additional problems with opening of the individual bags and does not provide for serially opening or self-opening of the bags as they are removed from the bag pack and from the rack.
More recently, the assignee of the present application has introduced a pack of star-seal type easy-opening handless or T-shirt type plastic bags for packaging grocery produce or the like and which is adapted to be suspended from the top of the bags of the pack by detachable tabs extending upwardly from each layer of the bag for mounting the bag pack on a rack. For easy-opening of these bags, at least the front two tabs of the eight superimposed tabs of each star-seal type bag in the pack include means for rendering these front two wall layers of each bag front-side-free. This construction allowed a user to grasp these front two layers of each eight-layer folded star-seal type bag and pull it forward to remove it from the rack. This bag pack construction is fully disclosed in assignee""s U.S. Pat. No. 5,941,393, the disclosure of which is incorporated herein by reference.
While the bag construction of this U.S. patent of assignee had been widely accepted by consumers, it has presented a number of problems with respect to manufacture thereof. The difficulty in manufacturing a bag pack of the type described in this patent involves the manufacture of the front-side-free feature. To produce the front-side-free feature, a cutting process must be utilized which requires (1) the separation of individual plies of the bag by some means so that the front two plies only can be cut, (2) transport of the bag and (3) collection of individual bags into a pack. Each of these steps adds complexity to the manufacturing process and causes additional expense in producing the bag packs.
Accordingly, it is an object of this invention to provide a pack of serially-arranged plastic bags of the star-seal type which overcomes the problems discussed above.
In accordance with this invention, it has been found that a pack of serially-arranged superimposed plastic bags of the star-seal type can be produced which are not front-side-free (providing easy opening of the bags), but which are self-opening by virtue of the following novel construction.
Each of the bags of the pack comprises integrally formed front and rear walls and gussetted side walls extending inwardly toward each other to terminate in close proximity to each other. These walls have top portions defining an open mouth. The front and rear walls and gussetted side walls are further folded-over onto each other along a longitudinal axis of the bag to define eight superimposed wall layers in the bag which includes a front layer, a rear layer and six intermediate layers. A seal of the xe2x80x9cstar-sealxe2x80x9d type secures the bottoms of the eight superimposed wall layers together to close the bottom of the bag.
Mounting tabs form a part of the top portions of each of the eight wall layers of each bag and are in superimposed positions. Each mounting tab includes an aperture for mounting the tabs on a tab retaining device of a rack in a non-front-side-free manner. Each of the tabs includes means rendering the tab detachable and providing a predetermined detaching strength.
In one embodiment of the invention, the mounting tabs are detachable from the tab retaining device of the rack and provide a predetermined detaching strength to prevent premature tearing of the tab. This is accomplished by providing a means for propagating a tear from the tab mounting aperture to the top of the tab and which is preferably in the form of a V-shaped cut-out in the top of the tab over the tab mounting aperture and a nick formed in the tab and extending from the V-shaped cut-out toward the tab mounting aperture.
In another embodiment of this invention, the mounting tabs extend upwardly from the top portion of each of the eight wall layers of each bag and are detachable from the bags remaining on the tab retaining device of the rack and preferably include a neck portion which is narrower than the remaining portion of the tab and connects the tab to the respective bag wall layer. A means for propagating a tear across the tab preferably comprises a slit extending across a portion of the dimension of the neck portion of the tab and allows the tearing off of the tab from the bag while retaining sufficient strength in the tab to prevent premature tearing off of the tab and to provide a predetermined detaching strength for the tab.
The bag pack of this invention further includes a frangible bond between the rear layer and the front layer of each successive bag in the pack. This frangible bond has a predetermined strength which is (1) greater than the predetermined detaching strength of two of the tabs and (2) weaker than the detaching strength of the remaining six tabs of each bag, to allow the leading bag of the pack (when pulled by a user for removal) to disengage from the pack, while (before disengagement) pulling the succeeding bag in the pack to cause detaching of the two leading tabs for self-opening of the succeeding bag. This frangible bond preferably comprises a corona treatment on the front and rear layers of each of the folded bags and at least one (preferably a plurality) localized compressed area extending transversely through the bag pack in the top portions of the bag such that the bag pack has a decreased thickness in the compressed area and wherein the adjacent corona treated front and rear layers of successive bags in the compressed area are adhered together by a corona-induced pressure bond and adjacent intermediate layers in the compressed area are not appreciably adhered together.
The bag pack preferably includes means for aiding in maintaining the bags in the pack in substantial registration in the form of one or more cold weld areas piercing and extending transversely through said bag pack or in the form of a heat seal compression bond area through the superimposed mounting tabs.